...for rooting plumeria cuttings, and everyone should have one! Cuttings can rot easily in cold damp soil even if the soil is warm in the day time. In the summertime, you can get by without one because the hot cement, concrete, or gravel substitutes nicely, but in fall, winter, and spring, bottom heat is essential for rooting plumeria cuttings. The potting soil should be at 80 degrees or higher for rooting a plumeria cutting. A soil thermometer can also be purchased for less than $20 and will help ensure that your soil is the right temperature for rooting. Some people even use a used water bed heater as a substitute for a heat mat. Seeds and seedlings are also happy on a nice warm surface.
My friend Roger over at PlumeriaPals posted this information, and I'm going to re-post it here. Also, two other links are also listed for heat mats and accessories.
10"x20" Heat Mat $22.95pad
20"x20" Heat Mat $34.95pad
20"x48" Heat Mat $64.95pad
Heat Mat Thermostat $34.95
Seedling Heat Mats http://www.discount-hydro.com/cloning.asp
The Seedling Heat Mat comes in three convenient sizes,
10" x 20" (Holds 1 standard propagation tray), 20" x
20" (holds 2 standard propagation trays) and a 48" x
20" (holds up to 4 trays) with lighting and watering
instructions printed directly on the mat. Tray spacer
feet are included. This mat keeps the rooting area
about 10 degrees warmer than room temperature. For
more precise temperature control, a Heat Mat
Thermostat is available.
$ 24.95 - 10" x 20" Heat Mats
$ 34.95 - 20" x 20" Heat Mats
$ 59.95 - 48" x 20" Heat Mats
$ 34.95 - Heating Mat Thermostat